Phytoplankton,not allochthonous carbon,sustains herbivorous zooplankton production

Terrestrial organic matter inputs have long been thought to play an important role in aquatic food web dynamics. Results from recent whole lake ¹³C addition experiments suggest terrestrial particulate organic carbon (t-POC) inputs account for a disproportionate portion of zooplankton production. For example, several studies concluded that although t-POC only represented ≈20% of the flux of particulate carbon available to herbivorous zooplankton, this food source accounted for ≈50% of the C incorporated by zooplankton. We tested the direct dietary impact of t-POC (from the leaves of riparian vegetation) and various phytoplankton on Daphnia magna somatic growth, reproduction, growth efficiency, and lipid composition. By itself, t-POC was a very poor quality resource compared to cryptophytes, diatoms, and chlorophytes, but t-POC had similar food quality compared to cyanobacteria. Small additions of high quality Cryptomonas ozolinii to t-POC-dominated diets greatly increased Daphnia growth and reproduction. When offered alone, t-POC resulted in a Daphnia growth efficiency of 5 ± 1%, whereas 100% Cryptomonas and Scenedesmus obliquus diets resulted in growth efficiencies of 46 ± 8% (± SD) and 36 ± 3%, respectively. When offered in a 50:50 mixed diet with Cryptomonas or Scenedesmus, the t-POC fraction resulted in a partial growth efficiency of 22 ± 9% and 15 ± 6%, respectively. Daphnia that obtained 80% of their available food from t-POC assimilated 84% of their fatty acids from the phytoplankton component of their diet. Overall, our results suggest Daphnia selectively allocate phytoplankton-derived POC and lipids to enhance somatic growth and reproduction, while t-POC makes a minor contribution to zooplankton production.     

Trophic cascades promote threshold-like shifts in pelagic marine ecosystems

Fisheries can have a large impact on marine ecosystems, because the effects of removing large predatory fish may cascade down the food web. The implications of these cascading processes on system functioning and resilience remain a source of intense scientific debate. By using field data covering a 30-year period, we show for the Baltic Sea that the underlying mechanisms of trophic cascades produced a shift in ecosystem functioning after the collapse of the top predator cod. We identified an ecological threshold, corresponding to a planktivore abundance of ≈17 × 10¹⁰ individuals, that separates 2 ecosystem configurations in which zooplankton dynamics are driven by either hydroclimatic forces or predation pressure. Abundances of the planktivore sprat above the threshold decouple zooplankton dynamics from hydrological circumstances. The current strong regulation by sprat of the feeding resources for larval cod may hinder cod recovery and the return of the ecosystem to a prior state. This calls for the inclusion of a food web perspective in management decisions.     

Filtration of submicrometer particles by pelagic tunicates

Salps are common in oceanic waters and have higher per-individual filtration rates than any other zooplankton filter feeder. Although salps are centimeters in length, feeding via particle capture occurs on a fine, mucous mesh (fiber diameter d ∼0.1 μm) at low velocity (U = 1.6 ± 0.6 cm·s⁻¹, mean ± SD) and is thus a low Reynolds-number (Re ∼10⁻³) process. In contrast to the current view that particle encounter is dictated by simple sieving of particles larger than the mesh spacing, a low-Re mathematical model of encounter rates by the salp feeding apparatus for realistic oceanic particle-size distributions shows that submicron particles, due to their higher abundances, are encountered at higher rates (particles per time) than larger particles. Data from feeding experiments with 0.5-, 1-, and 3-μm diameter polystyrene spheres corroborate these findings. Although particles larger than 1 μm (e.g., flagellates, small diatoms) represent a larger carbon pool, smaller particles in the 0.1- to 1-μm range (e.g., bacteria, Prochlorococcus) may be more quickly digestible because they present more surface area, and we find that particles smaller than the mesh size (1.4 μm) can fully satisfy salp energetic needs. Furthermore, by packaging submicrometer particles into rapidly sinking fecal pellets, pelagic tunicates can substantially change particle-size spectra and increase downward fluxes in the ocean.     

Utility of the “Surprise” Question to Identify Dialysis Patients with High Mortality

Background and objectives: Dialysis patients are increasingly characterized by older age, multiple comorbidities, and shortened life expectancy. This study investigated whether the “surprise” question, “Would I be surprised if this patient died in the next year?” identifies patients who are at high risk for early mortality.Design, setting, participants, & measurements: This prospective cohort study of 147 patients in three hemodialysis dialysis units classified patients into “yes” and “no” groups on the basis of the “surprise” question response and tracked patient status (alive or dead) at 12 mo. Demographics, Charlson Comorbidity Index score, and Karnofsky Performance Status score were measured.Results: Initially, 34 (23%) patients were classified in the “no” group. Compared with the 113 patients in the “yes” group, the patients in the “no” group were older (72.5 ± 12.8 versus 64.5 ± 14.9), had a higher comorbidity score (7.1 ± 2.3 versus 5.8 ± 2.1), and had a lower performance status score (69.7 ± 17.1 versus 81.6 ± 15.8). At 12 mo, 22 (15%) patients had died; the mortality rate for the “no” group was 29.4% and for the “yes” group was 10.6%. The odds of dying within 1 yr for the patients in the “no” group were 3.5 times higher than for patients in the “yes” group, (odds ratio 3.507, 95% CI 1.356 to 9.067, P = 0.01).Conclusions: The “surprise” question is effective in identifying sicker dialysis patients who have a high risk for early mortality and should receive priority for palliative care interventions.Incident dialysis patients are increasingly characterized by older age, a large number of comorbid illnesses, and a high symptom burden (1). They have a significantly shortened life expectancy and an overall mortality rate more than eight times that of the general Medicare population (2). Researchers and an expert panel have noted the need for improved palliative care for the US dialysis population (3–6). Palliative care begins with establishing the goals of care (7), and estimating the prognosis of dialysis patients sets the context for discussing goals (8–10).The “surprise” question, “Would I be surprised if this patient died in the next 12 mo?” has been recognized as an innovation to improve end-of-life care by identifying patients who have a poor prognosis and who are appropriate for palliative care (11–13). The “surprise” question has been tested and found to be effective in a primary care population in the Franciscan Health System in Tacoma, WA (11), but not in chronic disease populations such as those with kidney disease. The purpose of this study was to study the clinical characteristics of dialysis patients who were classified into a “no, I would not be surprised” group in response to the “surprise” question and to determine the effectiveness of the use of the “surprise” question to identify a subset of dialysis patients who have a high risk for early death and should receive priority for palliative care interventions.     

High saturated-fat and low-fibre intake: a comparative analysis of nutrient intake in individuals with and without type 2 diabetes

Objective:

The aim of dietary modification, as a cornerstone of type 2 diabetes (T2DM) management, is to optimise metabolic control and overall health. This study describes food and nutrient intake in a sample of adults with T2DM, and compares this to recommendations, and to intake in age, sex, body mass index (BMI) and social-class matched adults without T2DM.

Design:

A cross-sectional analysis of food and nutrient intake in 124 T2DM individuals (64% male; age 57.4±5.6 years, BMI 32.5±5.8 kg m⁻²) and 124 adults (age 57.4±7.0 years, BMI 31.2±5.0 kg m⁻²) with no diabetes (ND) was undertaken using a 4-day semiweighed food diary. Biochemical and anthropometric variables were also measured.

Results:

While reported energy intake was similar in T2DM vs ND (1954 vs 2004 kcal per day, P=0.99), T2DM subjects consumed more total-fat (38.8% vs 35%, P⩽0.001), monounsaturated-fat (13.3% vs 12.2% P=0.004), polyunsaturated-fat (6.7% vs 5.9% P<0.001) and protein (18.6% vs 17.5%, P⩽0.01). Both groups exceeded saturated-fat recommendations (14.0% vs 13.8%). T2DM intakes of carbohydrate (39.5% vs 42.9%), non-milk sugar (10.4% vs 15.0%) and fibre (14.4 vs 18.9 g) were significantly lower (P<0.001). Dietary glycaemic load (GL) was also lower in T2DM (120.8 vs 129.2; P=0.02), despite a similar glycaemic index (59.7 vs 60.1; P=0.48). T2DM individuals reported consuming significantly more wholemeal/brown/wholegrain breads, eggs, oils, vegetables, meat/meat products, savoury snacks and soups/sauces and less white breads, breakfast cereals, cakes/buns, full-fat dairy, chocolate, fruit juices, oily fish and alcohol than ND controls.

Conclusion:

Adults with T2DM made different food choices to ND adults. This resulted in a high saturated-fat diet, with a higher total-fat, monounsaturated-fat, polyunsaturated-fat and protein content and a lower GL, carbohydrate, fibre and non-milk sugar content. Dietary education should emphasise and reinforce the importance of higher fibre, fruit, vegetable and wholegrain intake and the substitution of monounsaturated for saturated-fat sources, in energy balanced conditions.     

Pellet microfossils: Possible evidence for metazoan life in Early Proterozoic time

Microfossils resembling fecal pellets occur in acid-resistant residues and thin sections of Middle Cambrian to Early Proterozoic shale. The cylindrical microfossils average 50 × 110 μm and are the size and shape of fecal pellets produced by microscopic animals today. Pellets occur in dark gray and black rocks that were deposited in the facies that also preserves sulfide minerals and that represent environments analogous to those that preserve fecal pellets today. Rocks containing pellets and algal microfossils range in age from 0.53 to 1.9 gigayears (Gyr) and include Burgess Shale, Greyson and Newland Formations, Rove Formation, and Gunflint Iron-Formation. Similar rock types of Archean age, ranging from 2.68 to 3.8 Gyr, were barren of pellets. If the Proterozoic microfossils are fossilized fecal pellets, they provide evidence of metazoan life and a complex food chain at 1.9 Gyr ago. This occurrence predates macroscopic metazoan body fossils in the Ediacaran System at 0.67 Gyr, animal trace fossils from 0.9 to 1.3 Gyr, and fossils of unicellular eukaryotic plankton at 1.4 Gyr.     

Measurement and modeling of the transient difference between blood and subcutaneous glucose concentrations in the rat after injection of insulin

The kinetics of the fall in subcutaneous fluid glucose concentration in anesthetized rats (n = 7) after intravenous injection of insulin (0.5 units/kg) was studied by using 5 × 10⁻⁴ cm² active area, <150-sec 10–90% response time, amperometric glucose sensors. The onset of the decline in the subcutaneous glucose concentration was delayed and statistically different (P < 0.001) from that in blood (8.9 ± 2.1 min vs. 3.3 ± 0.5 min). Similarly, the rate of drop in glucose concentration between 6 and 20 min after the insulin injection was different for subcutaneous tissue (3.9 ± 1.3 mgdl⁻¹ min⁻¹) and blood (6.8 ± 2.0 mgdl⁻¹min⁻¹) (P = 0.003). The hypoglycemic nadir in subcutaneous fluid occurred 24.5 ± 6.8 min after that in the blood (P < 0.001). A “forward” mass-transfer model, predicting the subcutaneous glucose concentration from the blood glucose concentrations and an “inverse” model, predicting the blood glucose concentration from the subcutaneous glucose concentration were derived. By using an algorithm based on the latter, the average discrepancy between the measured blood glucose concentration and that estimated from the subcutaneous measurement through the entire 4-hr experiment was reduced from 22.9% to 11.1% (P = 0.025). The maximum discrepancy during the 40-min period after the injection of insulin was reduced from 84.1% to 29.3% (P = 0.006).     

Transplant Tourism in the United States: A Single-Center Experience

Background and objectives: Transplant “tourism” typically refers to the practice of traveling outside the country of residence to obtain organ transplantation. This study describes the characteristics and outcomes of 33 kidney transplant recipients who traveled abroad for transplant and returned to University of California, Los Angeles (UCLA) for follow-up.Design, settings, participants, & measurements: Posttransplantation outcomes were compared between tourists and a matched cohort of patients who underwent transplantation at UCLA (matched for age, race, transplant year, dialysis time, previous transplantation, and donor type). Median follow-up time was 487 d (range 68 to 3056).Results: Compared with all patients who underwent transplantation at UCLA, tourists included more Asians and had shorter dialysis times. Most patients traveled to their region of ethnicity with the majority undergoing transplantation in China (44%), Iran (16%), and the Philippines (13%). Living unrelated transplants were most common. Tourists presented to UCLA a median of 35 d after transplantation. Four patients required urgent hospitalization, three of whom lost their grafts. Seventeen (52%) patients had infections, with nine requiring hospitalization. One patient lost her graft and subsequently died from complications related to donor-contracted hepatitis B. One-year graft survival was 89% for tourists and 98% for the matched UCLA cohort (P = 0.75). The rate of acute rejection at 1 yr was 30% in tourists and 12% in the matched cohort.Conclusions: Tourists had a more complex posttransplantation course with a higher incidence of acute rejection and severe infectious complications.The demand for kidney transplantation continues to increase (1,2). Some patients opt to explore the option of kidney transplantation outside their country of residence (3). In the United States, the implications of this practice, often termed “transplant tourism,” remain largely unknown.The observation of an increasing trend of patients who return from transplantations that are performed abroad led us to review the experience and outcomes with transplant tourism among patients who were followed in the UCLA Kidney Transplant program. We describe the characteristics and posttransplantation outcomes of patients who sought a transplant abroad and then returned to be followed at UCLA.     

Climate forcings in the Industrial era

The forcings that drive long-term climate change are not known with an accuracy sufficient to define future climate change. Anthropogenic greenhouse gases (GHGs), which are well measured, cause a strong positive (warming) forcing. But other, poorly measured, anthropogenic forcings, especially changes of atmospheric aerosols, clouds, and land-use patterns, cause a negative forcing that tends to offset greenhouse warming. One consequence of this partial balance is that the natural forcing due to solar irradiance changes may play a larger role in long-term climate change than inferred from comparison with GHGs alone. Current trends in GHG climate forcings are smaller than in popular “business as usual” or 1% per year CO₂ growth scenarios. The summary implication is a paradigm change for long-term climate projections: uncertainties in climate forcings have supplanted global climate sensitivity as the predominant issue.     

Efficient Removal of Nonylphenol Contamination from Water Using Optimized Magnesium Silicate

Nonylphenol (NP) is considered to be an environmentally toxic, endocrine-disrupting chemical that affects humans and ecosystems. Adsorption is one of the most promising approaches for the removal of nonylphenol contamination from water. Herein, in order to design an adsorbent with high adsorption capacity, magnesium silicate with different Mg/Si ratios was successfully synthesized by a sol–gel method at 60 °C. Magnesium silicate with a Mg/Si ratio of 1:6 was found to possess the best adsorption performance, with maximum 4−NP sorption 30.84 mg/g under 25 °C and 0.2 g/L adsorbent dose. The adsorption was negatively affected by increasing adsorbent dose and temperature. The kinetics and isotherm of 4−NP adsorption by Mg/Si were well described by the pseudo−second−order and Sips model, respectively, and behavior was proven to be physisorption−enhanced by a chemical effect. Detailed characterization by XRD, BET, and SEM confirmed that the magnesium silicate possesses an amorphous, mesoporous structure. The study will contribute to the applicability of cheap magnesium silicate for removal of NP contamination in water.     

In Crescentic IgA Nephropathy,Fractional Excretion of IgG in Combination with Nephron Loss Is the Best Predictor of Progression and Responsiveness to Immunosuppression

Background and objectives: The aim of this study was to evaluate the relationship between proteinuric markers (urinary excretion of IgG, α2-macroglobulin, α1-microglobulin) and serum creatinine (sCr), histologic lesions, progression, and immunosuppression responsiveness in crescentic IgA nephropathy.Design, setting, participants, & measurements: Fractional excretion of IgG (FEIgG) and of α1-microglobulin and urinary excretion of α2-macroglobulin were evaluated in 37 patients, 23 treated with steroids and cyclophosphamide. For assessment of the effective tubular load of proteins in surviving nephrons, new markers that take into account not only the absolute excretion value but also nephron loss were obtained dividing proteinuric markers for percentage of nonobsolescent glomeruli (surviving glomeruli [SG]). For each parameter, low- and high-risk groups were defined according to cutoffs with the highest sensitivity and specificity for progression (ESRD/doubling sCr) assessed by receiver operating characteristic analysis; follow up was 60 ± 40 mo.Results: FEIgG/SG is the most powerful progression predictor: 5 versus 83% in all patients; in treated patients, 0 versus 89%, increased to 0 versus 100% by sCr and FEIgG/SG in combination (low risk: both markers or only one below cutoff (n = 15); high risk: both markers above cutoff (n = 8). The nonprogressors showed at last observation 65% proteinuria reduction and 10% sCr reduction.Conclusions: In crescentic IgA nephropathy, FEIgG/SG, which evaluates altered size selectivity in relation to nephron loss, is the best progression predictor. In treated patients, progression prediction was increased by FEIgG/SG and sCr in combination. Treatment may be restricted to low-risk patients.The crescentic variant of IgA nephropathy (cIgAN) with histologic features similar to those observed in Schönlein-Henoch or ANCA-related renal vasculitis is characterized by more frequent nephrotic syndrome and renal functional impairment, more severe global glomerulosclerosis and tubulointerstitial damage, and higher rate of progression to renal death in comparison with noncrescentic IgAN (1,2). Treatment that is appropriate to prevent progression has not been clearly identified. Few small, nonrandomized studies have evaluated the efficacy of intravenous and oral steroids and oral or intravenous cyclophosphamide (3–9), but no firm conclusions can be drawn about the best type of therapy and the clinical and laboratory features that are able to predict treatment responsiveness. In glomerulonephritis, “crucial to the question of therapy is the ability to predict outcome in a patient as early and accurately as possible and ideally based on modifiable factors. Only after this assessment is made can we logically determine the risk versus benefit of treatments” (10). Proteinuria is one of the most powerful predictors of progression in IgAN; surprisingly, no one study has analyzed in cIgAN the urinary excretion of single proteins to evaluate their relationship with renal function and histologic lesions and to assess whether some “glomerular” and/or “tubular” component of proteinuria predicts outcome and therapy responsiveness better than other, widely known predictors (renal functional impairment, proteinuria, global glomerulosclerosis, extent of tubulointerstitial damage). The aim of this study was to analyze in 37 patients with cIgAN the fractional excretion of IgG (FEIgG) and α1-microglobulin (FEα1m) and urinary excretion of α2-macroglobulin (uα2m/g uCr) and their relationship with renal function, histologic lesions, functional outcome, and responsiveness to therapy.     

Comparison of the effects of 52 weeks weight loss with either a high-protein or high-carbohydrate diet on body composition and cardiometabolic risk factors in overweight and obese males

Background:

A high-protein (HP), low-fat weight-loss diet may be advantageous for improving cardiometabolic health outcomes and body composition. To date, only limited research has been conducted in male participants.

Objective:

To evaluate the medium to long-term effects of two, low-fat, hypocaloric diets differing in carbohydrate:protein ratio on body composition and cardiometabolic health outcomes in overweight and obese males.

Design:

One hundred and twenty males (age 50.8±9.3 (s.d.) years, body mass index 33.0±3.9 kg m⁻²) were randomly assigned and consumed a low-fat, isocaloric, energy-restricted diet (7 MJ per day) with either HP (protein:carbohydrate:fat %energy, 35:40:25) or high carbohydrate (HC; 17:58:25). Body weight, body composition and cardiometabolic risk factors were assessed at baseline and after 12 and 52 weeks.

Results:

Sixty-eight participants completed the study (HP, n=33; HC, n=35). At 1 year both the groups experienced similar reductions in body weight (HP, −12.3±8.0 kg (−12%); HC, −10.9±8.6 kg (−11%); P=0.83 time × group interaction) and fat mass (−9.9±6.0 kg (−27%) vs −7.3±5.8 kg (−22%); P=0.11). Participants who consumed the HP diet lost less fat-free mass (−2.6±3.7 kg (−4%) vs −3.8±4.7 kg (−6%); P<0.01). Both groups experienced similar increases in high-density lipoprotein cholesterol (8%) and reductions in total cholesterol (−7%), low-density lipoprotein cholesterol (−9%), triglycerides (−24%), glucose (−3%), insulin (−38%), blood pressure (−7/−12%) and C-reactive protein (−29%), (P⩾0.14).

Conclusion:

In overweight and obese men, both a HP and HC diet reduced body weight and improved cardiometabolic risk factors. Consumption of a HP diet was more effective for improving body composition compared with an HC diet.     

From the Cover: Thick-shelled,grazer-protected diatoms decouple ocean carbon and silicon cycles in the iron-limited Antarctic Circumpolar Current

Diatoms of the iron-replete continental margins and North Atlantic are key exporters of organic carbon. In contrast, diatoms of the iron-limited Antarctic Circumpolar Current sequester silicon, but comparatively little carbon, in the underlying deep ocean and sediments. Because the Southern Ocean is the major hub of oceanic nutrient distribution, selective silicon sequestration there limits diatom blooms elsewhere and consequently the biotic carbon sequestration potential of the entire ocean. We investigated this paradox in an in situ iron fertilization experiment by comparing accumulation and sinking of diatom populations inside and outside the iron-fertilized patch over 5 wk. A bloom comprising various thin- and thick-shelled diatom species developed inside the patch despite the presence of large grazer populations. After the third week, most of the thinner-shelled diatom species underwent mass mortality, formed large, mucous aggregates, and sank out en masse (carbon sinkers). In contrast, thicker-shelled species, in particular Fragilariopsis kerguelensis, persisted in the surface layers, sank mainly empty shells continuously, and reduced silicate concentrations to similar levels both inside and outside the patch (silica sinkers). These patterns imply that thick-shelled, hence grazer-protected, diatom species evolved in response to heavy copepod grazing pressure in the presence of an abundant silicate supply. The ecology of these silica-sinking species decouples silicon and carbon cycles in the iron-limited Southern Ocean, whereas carbon-sinking species, when stimulated by iron fertilization, export more carbon per silicon. Our results suggest that large-scale iron fertilization of the silicate-rich Southern Ocean will not change silicon sequestration but will add carbon to the sinking silica flux.Diatoms—silica-shelled unicellular phytoplankton—are major exporters of organic carbon from the surface to the deep ocean and sediments and, hence, influence ocean nutrient cycles and atmospheric CO₂ levels (1, 2). However, silicate concentrations, for which diatoms have an obligate demand, vary widely over the nutrient-rich regions of the oceans (3). This is largely due to processes decoupling silicon cycling from that of other nutrients and carbon in surface waters of the Antarctic Zone (AZ), the southernmost belt of the Antarctic Circumpolar Current (ACC) (4). Thus, Si concentrations decline across the AZ from >70 mmol Si⋅m⁻³ in upwelling waters along its southern boundary (the Antarctic Divergence) (5) to <5 mmol Si⋅m⁻³ along the Antarctic Polar Front (APF) (6). The corresponding decline in nitrate is much smaller, from 30 to 23 mmol N⋅m⁻³. The resulting Si/N export ratio of 9/1 is much higher than the average diatom Si/N ratio of ∼1/1 (7, 8). The paradox (9) can partly be explained by increasing Si/N ratios with iron deficiency recorded in many species (10–13) in addition to the exceptionally thick frustules of some ACC diatom species (14), which can reach Si/N ratios of >4:1 in Fragilariopsis kerguelensis (15).A portion of the silica shells (frustules) sinking out of the northward-propagating surface Ekman layer dissolves in the southward-propagating deep water and is returned as Si to the surface in upwelling water along the Antarctic Divergence (1). This vertical recycling loop between surface and deep water supports growth of thick-shelled diatoms in the surface and functions as a global ocean silicon trap in the deep-water column. Another portion, mainly comprising robust frustules of comparatively few species, of which Fragilariopsis kerguelensis and Thalassiothrix antarctica are particularly common (16–18), is buried as diatom ooze in sediments underlying the iron-limited ACC, which functions as a major global silicon sink (19), accounting for 42–48% of the total marine silica removal (20). In contrast, the sediments underlying productive regions in the ACC, where phytoplankton blooms fertilized by iron input from land masses (21, 22), shelf sediments or dust occur regularly (23), have 10-fold higher carbon contents (>2% C of dry matter) (24), and are dominated by spores of the ubiquitous diatom genus Chaetoceros (25, 26).The massive removal of silicon relative to nitrogen from the surface layer by the diatoms of the low-productive, iron-limited AZ ecosystem implies that, in addition to the heavy silicification of ACC diatoms (14), a significant proportion of their nitrogen demand will have to be provided by a highly efficient recycling system in the surface layer (27). In contrast to phytoplankton, copepod-dominated zooplankton stocks of high-nutrient, low-chlorophyll (HNLC) regions of the oceans are comparatively large (28, 29). In fact, their grazing pressure was considered to control phytoplankton biomass in HNLC regions before iron limitation was firmly established (30). It has since been hypothesized that copepod feeding and defecation are part of the recycling system (31) and that the phytoplankton species that accumulate biomass in the face of heavy grazing pressure will have evolved some form of defense (32), most likely the heavily silicified frustules characteristic of ACC diatoms (14).As the Si-depleted northern ACC surface layer is the major source of nutrients upwelling in low latitudes (4), Si retention in the ACC constrains diatoms from forming blooms over large, nutrient-rich areas of the ocean (3) with far-reaching repercussions on food webs and ocean carbon sequestration. A better understanding of the deep water silicon trap and sedimentary sink is necessary to explain functioning of the glacial Southern Ocean (33) and its impact on CO₂ drawdown, but also to predict the response of Southern Ocean biota to large-scale and long-term artificial iron fertilization (34). Ocean iron fertilization experiments provide the necessary conditions for the quantitative investigation of these mechanisms because they simulate the effect of natural iron input on pelagic ecosystems with their full complement of grazers and pathogens (34).     

Performance of Procedures by Nephrologists and Nephrology Fellows at U.S. Nephrology Training Programs

Background and objectives: Some procedures (e.g., placement of temporary hemodialysis catheters and kidney biopsies) are required in nephrology fellowship training. Others (e.g., placement of tunneled hemodialysis catheters, ultrasonography, and hemodialysis access interventions) are not required but are performed at some centers. To assess the procedures performed by nephrologists and nephrology fellows at U.S. adult nephrology training programs and the number of procedures required for fellow competency, a survey was conducted of all such training programs.Design, setting, participants, & measurements: An on-line survey was e-mailed to the directors of all U.S. adult nephrology fellowship programs in October to November 2007.Results: Responses were received from 93 of 136 programs. Nephrologists and nephrology trainees perform native and transplant kidney biopsies in 98% to 99% of programs and, in about half of programs, also perform the ultrasound guidance. Diagnostic ultrasounds are performed at fewer programs. Temporary dialysis catheters are inserted at nearly all programs. Tunneled hemodialysis catheters and peritoneal dialysis catheters are placed at ≤20% of programs. Interventional procedures on hemodialysis access are performed at 13% to 21% of programs. Continuous renal replacement therapy is performed at 99% of programs, plasmapheresis at 40%. Many programs either do not specify a minimum number of supervised procedures that need to be performed to demonstrate competence or require a very limited number.Conclusions: Core procedures are performed at almost all programs. Experience and training in other procedures are variable. Many programs have limited requirements for the number of procedures trainees need to perform to demonstrate competence.Care of patients with kidney disease involves a number of imaging and invasive procedures. “Core” procedures, such as percutaneous renal biopsy and insertion of temporary hemodialysis catheters, have traditionally been performed by nephrologists but increasingly are performed by other specialists. The involvement of nephrologists in other procedures, such as diagnostic ultrasound, placement of tunneled hemodialysis and peritoneal dialysis catheters, creation of arteriovenous fistulas, and interventions on hemodialysis grafts and fistulas, is limited but may be changing. The number of nephrologists performing dialysis access procedures (interventional nephrologists) in this country is growing, and diagnostic ultrasonography, which is routinely practiced by nephrologists in several European countries, is also becoming more commonplace among nephrologists in the United States. Studies have documented the competence of nephrologists in performing these procedures and the improvements in patient care that result (1–4).The continued performance of “core” procedures by future nephrologists as well as the introduction of additional procedures into nephrology requires that these skills be obtained in nephrology training programs. However, procedures are often not a major focus in most programs, and many faculty may feel ill qualified to teach them. To assess what types of procedures are performed by nephrology fellows and faculty at U.S. adult nephrology training programs, an electronic survey was conducted of all such programs. The results of that survey, reported here, demonstrate tremendous variability between programs in the performance of procedures by nephrologists, trainee involvement in the procedures, and criteria for assessing the competence of trainees.     

Limited oral bioavailability and active epithelial excretion of paclitaxel (Taxol) caused by P-glycoprotein in the intestine

In mice, the mdr1a and mdr1b genes encode drug-transporting proteins that can cause multidrug resistance in tumor cells by lowering intracellular drug levels. These P-glycoproteins are also found in various normal tissues such as the intestine. Because mdr1b P-glycoprotein is not detectable in the intestine, mice with a homozygously disrupted mdr1a gene [mdr1a(−/−) mice] do not contain functional P-glycoprotein in this organ. We have used these mdr1a(−/−) mice to study the effect of gut P-glycoprotein on the pharmacokinetics of paclitaxel. The area under the plasma concentration-time curves was 2- and 6-fold higher in mdr1a(−/−) mice than in wild-type (wt) mice after i.v. and oral drug administration, respectively. Consequently, the oral bioavailability in mice receiving 10 mg paclitaxel per kg body weight increased from only 11% in wt mice to 35% in mdr1a(−/−) mice. The cumulative fecal excretion (0–96 hr) was markedly reduced from 40% (after i.v. administration) and 87% (after oral administration) of the administered dose in wt mice to below 3% in mdr1a(−/−) mice. Biliary excretion was not significantly different in wt and mdr1a(−/−) mice. Interestingly, after i.v. drug administration of paclitaxel (10 mg/kg) to mice with a cannulated gall bladder, 11% of the dose was recovered within 90 min in the intestinal contents of wt mice vs. <3% in mdr1a(−/−) mice. We conclude that P-glycoprotein limits the oral uptake of paclitaxel and mediates direct excretion of the drug from the systemic circulation into the intestinal lumen.     

The Surface of Nanoparticle Silicon as Studied by Solid-State NMR

The surface structure and adjacent interior of commercially available silicon nanopowder (np-Si) was studied using multinuclear, solid-state NMR spectroscopy. The results are consistent with an overall picture in which the bulk of the np-Si interior consists of highly ordered (“crystalline”) silicon atoms, each bound tetrahedrally to four other silicon atoms. From a combination of ¹H, ²⁹Si and ²H magic-angle-spinning (MAS) NMR results and quantum mechanical ²⁹Si chemical shift calculations, silicon atoms on the surface of “as-received” np-Si were found to exist in a variety of chemical structures, with apparent populations in the order (a) (Si–O–)₃Si–H > (b) (Si–O–)₃SiOH > (c) (HO–)_nSi(Si)_m(–OSi)_4−m−n ≈ (d) (Si–O–)₂Si(H)OH > (e) (Si–O–)₂Si(–OH)₂ > (f) (Si–O–)₄Si, where Si stands for a surface silicon atom and Si represents another silicon atom that is attached to Si by either a Si–Si bond or a Si–O–Si linkage. The relative populations of each of these structures can be modified by chemical treatment, including with O₂ gas at elevated temperature. A deliberately oxidized sample displays an increased population of (Si–O–)₃Si–H, as well as (Si–O–)₃SiOH sites. Considerable heterogeneity of some surface structures was observed. A combination of ¹H and ²H MAS experiments provide evidence for a substantial population of silanol (Si–OH) moieties, some of which are not readily H-exchangeable, along with the dominant Si–H sites, on the surface of “as-received” np-Si; the silanol moieties are enhanced by deliberate oxidation. An extension of the DEPTH background suppression method is also demonstrated that permits measurement of the T₂ relaxation parameter simultaneously with background suppression.     

Distribution of genes in the genome of Arabidopsis thaliana and its implications for the genome organization of plants

Previous work has shown that, in the large genomes of three Gramineae [rice, maize, and barley: 415, 2,500, and 5,300 megabases (Mb), respectively] most genes are clustered in long DNA segments (collectively called the “gene space”) that represent a small fraction (12–24%) of nuclear DNA, cover a very narrow (0.8–1.6%) GC range, and are separated by vast expanses of gene-empty sequences. In the present work, we have analyzed the small (ca. 120 Mb) nuclear genome of Arabidopsis thaliana and shown that its organization is drastically different from that of the genomes of Gramineae. Indeed, (i) genes are distributed over about 85% of the main band of DNA in CsCl and cover an 8% GC range; (ii) ORFs are fairly evenly distributed in long (>50 kb) sequences from GenBank that amount to about 10 Mb; and (iii) the GC levels of protein-coding sequences (and of their third codon positions) are correlated with the GC levels of their flanking sequences. The different pattern of gene distribution of Arabidopsis compared with Gramineae appears to be because the genomes of the latter comprise (i) many large gene-empty regions separating gene clusters and (ii) abundant transposons in the intergenic sequences of gene clusters. Both sequences are absent or very scarce in the Arabidopsis genome. These observations provide a comparative view of angiosperm genome organization.     

Surgical Management of Pulmonary Hydatid Cysts: Is Size an Important Prognostic Indicator?

Giant hydatid cysts of the lung (diameter, ≥10 cm) are considered more difficult to treat surgically than are smaller cysts. We reviewed our experience with giant pulmonary hydatid cysts, focusing on clinical symptoms, cystic location, extent of surgery, and postoperative complications, according to age, long-term results, and comparison with non-giant cysts. From January 1988 to January 2008, 537 patients underwent surgery for pulmonary hydatid cysts. We separated patients into 2 groups: patients who had cysts <10 cm (group A) and those who had giant cysts (group B). Group B comprised 75 patients (14%). Giant cysts were more common in younger patients (mean age, 30 vs 32 yr; P=0.014). The most frequent complaints were cough, chest pain, and dyspnea. Patients with giant cysts were more often symptomatic at presentation (96% vs 88%; P=0.04). In both groups, lower-lobe locations predominated. Parenchyma-saving operations were almost uniformly performed for each group; however, a higher percentage of patients in group B required anatomic resection (4% vs 1%; P=0.038). Fifty-seven patients (10%) also underwent resection of concomitant liver cysts. Cystic rupture occurred more frequently in group B than in group A (27% vs 15%; P=0.01). There were no deaths in either group, nor were there significant differences in morbidity between groups.In summary, giant hydatid cysts of the lung occurred more often in younger patients and were more often symptomatic at presentation. Regardless of size, the cysts could usually be surgically treated without lung resection, and size did not appear to influence short-term perioperative outcomes.Key words: Adolescent, adult, age distribution, age factors, aged, child, albendazole/therapeutic use, echinococcosis, hepatic/surgery, echinococcosis, pulmonary/surgery, Horner syndrome/etiology, hydatid cyst, middle age, retrospective studies, treatment outcomeHydatid cysts are the most common parasitic disease of the lungs. They are a major health problem in agricultural countries that lack satisfactory preventive medicine, environmental health, and veterinarian services. Hydatid disease is endemic in the eastern and southeastern regions of Turkey.¹ Hydatid cysts of 10 cm or greater in diameter are called “giant” cysts and traditionally have been considered to be more difficult to treat surgically—often requiring pulmonary resection. We aimed to retrospectively evaluate our institutional experience with surgically treated hydatid cysts to investigate whether cystic size is really an important factor in terms of clinical outcome.     

Management of chronic heart failure in the community: role of a hospital based open access heart failure service

Objective: To evaluate the role of an open access heart failure service based at a teaching hospital for the diagnosis and treatment optimisation of patients with heart failure in the community and to identify measures that may further enhance the effectiveness of such a service.

Subjects: 963 patients with suspected heart failure seen over an eight year period referred by their general practitioners to the cardiology department at a district general hospital.

Main outcome measures: Presence or absence of left ventricular systolic dysfunction (LVSD) (left ventricular ejection fraction < 50% on echocardiography), and determination of the risk factors and predictors of LVSD.

Results: The majority of the patients were women (60% v 40%) and elderly (mean age 68.8 years). On echocardiography, only 30.8% were found to have LVSD. Patients were more likely to have LVSD if they were men (42.3% v 23.1%, p < 0.001, relative risk (RR) 1.8), were > 60 years of age (33.5% v 20.8%, p < 0.001, RR 1.6), or had a history of diabetes (49.4% v 29.1%, p < 0.001, RR 1.7), ischaemic heart disease (36.5% v 29.1%, p = 0.04, RR 1.3), or atrial fibrillation (52.6% v 27.8%, p < 0.001, RR 1.9). An abnormal ECG (48.4% v 19.5%, p < 0.001, RR 2.5) and cardiothoracic ratio > 0.5 on chest radiograph (44.3% v 17.8%, p < 0.001, RR 2.5) were found to be good predictors of LVSD. A normal ECG (negative predictive value 80.5%) and a cardiothoracic ratio of < 0.5 (negative predictive value 82.2%) can be used as baseline measures to identify patients with lower risk of developing LVSD (combined negative predictive value 87.9%).

Conclusions: An open access heart failure clinic is effective for the diagnosis and management of chronic heart failure in community based patients. The presence of risk factors and simple baseline tests can be used to identify patients with LVSD in the community. The introduction of a protocol based on these findings into a referral system can improve the efficiency and cost effectiveness of such a service.